There are known for a wide variety of containers, various seals or closures which are sealed to the container around an opening to close the opening. To open the container, the seal has to be broken, providing an indication that the container has been opened, or possibly tampered with. Such seals or closures are used in a wide variety of containers, e.g. bottles of pharmaceuticals, foods, beverages, etc. In some cases their primary function is to provide an element of security, and an indication if the contents have been tampered with. For foods, they are frequently used to seal the foods, so as to maintain the freshness of the food and prevent contamination of the food.
The following U.S. patents all relate in general terms to seals for containers, and were considered during the preparation of this application.
713,824 (White) PA1 745,195 (Kimsey PA1 756,601 (Doremus) PA1 830,735 (Olsson) PA1 895,719 (Bradley) PA1 902,843 (Sheppard) PA1 1,073,071 (Hall) PA1 2,937,481 (Palmer) PA1 3,032,225 (Harding) PA1 3,317,068 (Betner) PA1 3,632,004 (Grimes) PA1 3,900,125 (Wyler) PA1 4,044,941 (Knudsen) PA1 4,155,439 (Fletcher et al) PA1 4,324,601 (Dembicki) PA1 4,423,819 (Cummings) PA1 4,442,129 (Niwa) PA1 4,462,502 (Luenser) PA1 4,469,754 (Hoh et al) PA1 4,501,371 (Smalley) PA1 4,514,248 (Cummings) PA1 4,526,562 (Knudsen et al) PA1 4,527,703 (Cummings) PA1 4,576,297 (Larson) PA1 4,579,240 (Ou-Yang) PA1 4,588,099 (Diez) PA1 4,625,875 (Carr) PA1 4,666,052 (Ou-Yang)
The seven earlier patents all relate generally to closures for bottles or containers including a shoulder or annular recess for a disk or card closure or the like, and many of them are particularly concerned with milk bottles. Some of these patents show tabs for assisting removal of the closure, but in general the structures are not suitable for simple, economical mass production, and they are not concerned with seals that can be bonded to the neck of a bottle.
In the White patent, a strip is secured to the disk closure by paste and its ends form tabs for removal of it.
Pat. No. 745,195 discloses a closure provided with an upper disk secured to the main disk and having a segment removed so it can be grasped. The drawings show a staple securing the two parts together.
Pat. No. 756,601 forms a tab by folding a single sheet of a certain shape.
In Pat. No. 830,735, there is disclosed a closure in which an upper disk is mounted over a lower disk and is larger. Whilst it is suggested that any suitable fastening could be employed, only shellac or a staple are disclosed.
Pat. No. 895,719 discloses a bottle or jar closure including a liftable pull tab in the centre of the disk.
Pat. No. 902,843 is concerned with a disk provided with a thread for lifting the closure.
The Hall patent again discloses a milk bottle seal, which includes a central flap for lifting the seal. A disadvantage with such an arrangement is the difficulty of bonding the two layers together whilst leaving the flap free.
The Palmer Pat. No. 2,937,418 is of some interest, as apparently being an early example of induction sealing of the closure to the neck of a bottle. However, it does not address the problem of providing any tab or the like to facilitate removal of the seal.
The Harding Pat. No. 3,032,225 discloses a combination closure which includes a tear-off cap. This is formed from thin aluminium and includes a tear-off tongue. No discussion is given as to how this would be formed. Experience with such tear-off tongues or tabs for aluminium foil closures indicates that they frequently do not function as intended. Often, instead of enabling the whole closure to be removed, a thin strip is torn from the middle of the closure.
The Betner Pat. No. 3,317,068 is concerned with tear-open sealed containers, and includes a multi-layer closure with a central pull tab.
The Grimes Pat. No. 3,632,004 tackles the problem of facilitating the removal of the closure or seal in a different manner. Here, a recess or notch is provided in the neck of the bottle, so that a portion of the closure overhangs it. This does not greatly facilitate removal of the closure. The user has to grasp a relatively small edge portion of the closure, and this is not practical for thin flexible seals. However, the notch is relatively small in width, so that again there is the potential for a foil seal to be torn, rather than removed as a whole.
The Wyler patent discloses a container for a pharmaceutical or cosmetic product with a foil closing the opening. This includes a tear-off flap. However, no great details are given as to how this would be formed.
The Carr et al Pat. No. 4,625,875 is primarily concerned with a tamper-evident closure. It does show a foil disk provided with a tab. This tab has to be folded over within the cap. No details are given as to how this would be formed or assembled.
The Fletcher et al Pat. No. 4,155,439 should also be noted. This is the only patent that discusses in detail the production of a flexible end closure with a folded pull tab. As shown in this patent, complex machinery is required to form the closure and fit it to the container. A circular table or platform is provided, on which the containers are placed. The table is then rotated, to move each container through numerous different stations. At each station a different operation is performed. The closure itself is stamped from a strip of foil, and then the tab has to be folded up on top of the main portion of it. A complex sequence is required to mount the closure to the container. To set up such machinery for a particular production run is time consuming and expensive.
Additional problems are encountered with this sort of technique. Firstly, the presence of the inwardly folded tab can affect the sealing by means of induction heating. Induction heating relies upon the generation of currents and hence heat in the foil. The presence of the tab affects the electrical properties locally, and can result in improper sealing. As discussed in an article by Bill Zito in the August , 1986 issue of Food and Drug Packaging, the current tends to follows the actual periphery of the tab. Also, the folded tab can stick to the inside of the cap, which then requires a silicone liner or the like. Additionally, the induction sealing technique relies upon the fact that the foil closure is pressed against the neck of the container by the cap. With the folded tab present, there may not be even pressure applied to the foil closure, which again can result in imperfect sealing.
Even if proper sealing is achieved, the tab itself often does not provide for reliable opening of the container. Ideally, the tab and the whole circular foil closure should be removable as one piece. In practice, when the tab is lifted to detach the foil from the bottle or container neck, only the portion of the foil adjacent to the tab becomes detached from the container. Then, the tab simply pulls away a strip of foil across the container. This then leaves the user to manually remove the remaining pieces of the foil. For many uses, it is quite undesirable for the user to have to insert his or her fingers into the neck of the container, as this can result in contamination. Such uses could be pharmaceutical products, and food and beverages dispensed at restaurants.
As suggested by the Fletcher et al patent and many other earlier proposals, a common technique for sealing a foil to the neck of a container is by induction heating. This requires the foil sealing member or closure to be inserted into a cap. The cap is then fitted, usually by screwing onto the neck of the container, so as to press the foil against the neck of the container. The neck of the container is then passed through an induction heater, which induces currents in the foil, melting an appropriate adhesive on the foil, causing it to bond to the neck of the bottle. One step in this process is the fitting of the foil into the cap, and the subsequent fitting of the cap to the neck of the container. For this purpose, the foil closure by itself must be capable of being retained within the cap. For simple aluminium foil sealing members or closures this does not always work perfectly. Aluminium has plastic characteristics; in other words, when the foil is pressed into a screw cap, the edges of the foil can deflect permanently as they pass over the screw threads. The edges of the foil do not snap-back into the grooves of the screw thread. Consequently, the foil can drop out before the cap is fitted to the container neck.
Accordingly, what is desired is a sealing member or closure which can be readily fitted to the neck of a container. It should be capable of being produced simply and economically on conventional machinery, without numerous complex forming operations. Ideally, it should be of uniform thickness throughout, and should be capable of uniform induction heating, so that it can be readily joined to the neck of a bottle by induction heating. Further, it is desirable that at least one edge portion should include elastic, as opposed to plastic properties, so that when inserted into a cap, it will snap-back into the grooves of the screw thread of the cap to retain the sealing member in position prior to induction heating and bonding.